Monday, September 18, 2017

medium | Two decades
ago, our research group made international headlines when we published
research showing that virtual reality systems could damage people’s
health.

Our
demonstration of side-effects was not unique — many research groups
were showing that it could cause health problems. The reason that our
work was newsworthy was because we showed that there were fundamental
problems that needed to be tackled when designing virtual reality
systems — and these problems needed engineering solutions that were
tailored for the human user.

In
other words, it was not enough to keep producing ever faster computers
and higher definition displays — a fundamental change in the way systems
were designed was required.

So why
do virtual reality systems need a new approach? The answer to this
question lies in the very definition of how virtual reality differs from
how we traditionally use a computer.

Natural
human behaviour is based on responses elicited by information detected
by a person’s sensory systems. For example, rays of light bouncing off a
shiny red apple can indicate that there’s a good source of food hanging
on a tree.

A
person can then use the information to guide their hand movements and
pick the apple from the tree. This use of ‘perception’ to guide ‘motor’
actions defines a feedback loop that underpins all of human behaviour.
The goal of virtual reality systems is to mimic the information that
humans normally use to guide their actions, so that humans can interact
with computer generated objects in a natural way.

The
problems come when the normal relationship between the perceptual
information and the corresponding action is disrupted. One way of
thinking about such disruption is that a mismatch between perception and
action causes ‘surprise’. It turns out that surprise is really
important for human learning and the human brain appears to be
engineered to minimise surprise.

This
means that the challenge for the designers of virtual reality is that
they must create systems that minimise the surprise experienced by the
user when using computer generated information to control their actions.

Of
course, one of the advantages of virtual reality is that the computer
can create new and wonderful worlds. For example, a completely novel
fruit — perhaps an elppa — could be shown hanging from a virtual tree.
The elppa might have a completely different texture and appearance to
any other previously encountered fruit — but it’s important that the
information used to specify the location and size of the elppa allows
the virtual reality user to guide their hand to the virtual object in a
normal way.

If
there is a mismatch between the visual information and the hand
movements then ‘surprise’ will result, and the human brain will need to
adapt if future interactions between vision and action are to maintain
their accuracy. The issue is that the process of adaptation may cause
difficulties — and these difficulties might be particularly problematic
for children as their brains are not fully developed.

This issue affects all forms of information presented within a virtual world (so hearing and
touch as well as vision), and all of the different motor systems (so
postural control as well as arm movement systems). One good example of
the problems that can arise can be seen through the way our eyes react
to movement.

In
1993, we showed that virtual reality systems had a fundamental design
flaw when they attempted to show three dimensional visual information.
This is because the systems produce a mismatch between where the eyes
need to focus and where the eyes need to point. In everyday life, if we
change our focus from something close to something far away our eyes
will need to change focus and alter where they are pointing.

The
change in focus is necessary to prevent blur and the change in eye
direction is necessary to stop double images. In reality, the changes in
focus and direction are physically linked (a change in fixation
distance causes change in the images and where the images fall at the
back of the eyes).